As far back as 1919, Iredell and Turner developed surgical diathermy, wherein current used to sever tissue is conducted to ground by the use of an indifferent electrode, also called a patient ground plate. Iredell and Turner demonstrated the effectiveness of a large, 72 square inch ground plate, where electrolytes, e.g. conductive pastes, gels or saline solutions are used at the skin/ground plate interface to lower resistance. The combination of a large ground plate with electrolytes is used to provide a low current density path to complete the electrosurgical circuit and minimize tissue heating at the skin/plate interface.
Large ground plates have drawbacks. They are not easily contoured to the body, and thus, relatively few body surface areas can accommodate them. When placed under a patient, for instance, it is difficult to know whether substantial plate/body contact is being maintained, particularly when the patient moves or is moved. Depending upon area contacted and method of applying the ground plate, circulation can be adversely affected, thus increasing the possibility of burns. The stiffness of plates and their infexibility and sharp edges can cause substantial discomfort to the patient, especially in the case of a prolonged operation. Also, a large patient ground plate inherently increases the possibility of accidental contact with surgical instruments or other metal objects that can result in a burn to the patient.
U.S. Pat. No. 3,848,600 issued to Patrick et al discloses a small electrode for use in electrosurgical procedures. This electrode comprises a metallic snap fastener terminal held spaced apart from the body by a polyurethane pad impregnated with a conductive electrolyte gel pad. The pad is held against the skin by a resilient sheet of foam plastic having a medical grade acrylic pressure sensitive adhesive coating on it for contact with the skin. U.S. Pat. No. 3,848,600 discloses many references of interest to electrosurgical procedures. That listing of references is herein incorporated by reference.
Although the small electrode of Patrick et al overcomes problems associated with the use of large surface area electrodes, their electrode does have disadvantages and inconveniences. The primary disadvantage resides in the utilization of the electrolytic gel which requires that the electrode be packaged individually with the gel in a liquid-tight container. This increased the over-all cost of the electrode due to the increases cost of packaging. Moreover, any premature exposure of the packaged electrode to atmospheric moisture conditions can result in the drying out of the gel. In use, gels are difficult and messy to apply, the during extended surgery, they can dry up and thereby lead to burns and other complications.
In addition to the above application disadvantages, the use of an electrolyte gel in contact with the skin, especially for long periods of time, can cause skin irritation and sores to develop. Another possible source of skin irritation during use of electrodes like that of Patrick et al is the adhesive which contacts a large area of the skin surrounding the area of the electrolyte contact. Thus, with electrodes of this type, the total skin contact area subject to irritation is substantially greater than the area to which the electrical connection is made since the area of electrical contact is separate and distinct from the area of securement. Moreover, because of this separation, the area of electrode contact is capable of surface to surface shifting which can impede the progress of the electrosurgical procedure.
Therefore, there is a need for an indifferent electrode for use with electrosurgical procedures which does not require the use of electrolytes such as conductive pastes, gels or saline solutions, which is relatively small in size and easily contoured toward various body surfaces to allow application to many sites, and which can be maintained securely attached to body surfaces without direct application of adhesives to body surfaces.